The present invention relates to a separation column for chromatography, a medium for solid phase extraction and a sample injection system for chromatography.
The solid phase microextraction (hereafter referred to as “SPME” or “solid phase extraction”) technique is the most powerful technique for the preliminary concentration of a sample in the analysis of organic compounds present in an aqueous sample using gas chromatography (GC). The SPME technique requires simpler operations and the use of a smaller amount of a solvent as compared with the conventional solvent extraction techniques and therefore, a wide variety of applications of the SPME/GC technique have been proposed. If a fussed silica fiber for use in the SPME technique is immersed in a sample solution, a substance or a compound to be analyzed (analyte) is extracted in a polymer coating present on the fiber. Subsequently, this fiber is introduced into a gas chromatograph through the injection port thereof, and then heated to thus desorb the analyte by the action of the heat. In contrast to the foregoing successful examples, there have been reported only a few attempts to combine the SPME technique with, for instance, the liquid chromatography (LC) technique or an electrokinetic separation technique for the analysis of a non-volatile compound. This is because the difficulty in the operations of the desorption of an analyte and the complicated mechanism of the on-line interface.
Recently, there has been developed another SPME technique by Pawliszyn et al. and more specifically, an in-tube SPME technique in which an SPME device can directly be connected to an LC separation device without using any interface device. This method makes use of an open tube GC-hollow capillary column as an extraction medium. In this case, if a sample solution (for instance, an aqueous solution) is passed through the capillary column using a microflow pump, an analyte present in the aqueous solution is extracted into a polymer coating within the hollow capillary. The analyte (or a solute) thus extracted can likewise be desorbed from the polymer coating by passing a small amount of an organic solvent through the hollow capillary. Thus, this method does not use any desorption device required for sending the extracted solute to a separation device. Therefore, this method permits the elimination of difficult or complicated operations and/or processes and the considerable reduction of the organic solvent required for the desorption of the analyte.
The inventors of this invention have adopted a wire-in-tube structure as an extraction hollow capillary for the analysis of a tricyclic antidepressant present in the human urine sample. This technique permits the reduction of the inner volume of the extraction hollow capillary tube by inserting a stainless steel wire into the hollow capillary, while remaining unchanged the surface area of the coating, which will come in contact with a sample solution. This constitution (or structure) would permit further improvement of the concentration effect as compared with the conventional in-tube type SPME technique. Moreover, this structure would suggest that an on-line wire-in-tube type SPME/LC device can be used for the high speed analysis of a variety of organic compounds present in the matrix of biological and environmental samples with high probability.
On the other hand, the analysis of low concentration phthalates present in the matrix of an aqueous sample is considered to be one of the most important subjects due to its estrogenic action. There have been investigated the quantitative analysis and the functions of phthalates as an endocrine function-disturbing substance, but there has still been desired for the development of an effective and rapid extraction-concentration technique for the practical analysis of an environmental water sample, which does not require the consumption of a large amount of a solvent.
Moreover, Japanese Un-Examined Utility Model Publication No. Sho 63-70080 discloses a separation column for chromatography, which comprises a hollow capillary and a stationary phase packed in the hollow capillary and comprising a collected body, which comprises cellulose acetate long fibers having an adsorbing ability selective towards a solute and arranged along the axial direction of the hollow capillary. This column employs cellulose acetate fibers as the long fibers and therefore, it can be used as a separation column for liquid chromatography, but it is difficult to use the same for gas chromatography. In addition, this publication never suggests that this column can be used as a medium for solid phase extraction, which is effective for the concentration of a liquid sample.